With recent technology developments and advances in microincision cataract surgery, increased emphasis has been placed on developing soft, foldable materials suitable for use in intraocular lenses which can be delivered through sub 2.0 mm incisions.
One class of the currently-known soft, foldable materials suitable for intraocular lenses is soft, hydrophobic acrylic materials, for example, those described in U.S. Pat. Nos. 4,834,750, 5,290,892, 5,331,073, 5,693,095, 5,922,821, 6,241,766, 6,245,106, 6,313,187, 6,353,069, 6,528,602, 6,653,422, 6,703,466, 6,780,899, 6,806,337, 6,872,793, 7,585,900, 7,652,076, 7,714,039, 7,790,824, 7,790,825, 7,799,845, 7,847,046, 8,058,323, 8,362,177, 8,466,209, 8,449,610, 8,557,892 (herein incorporated by references in their entireties). Those reported acrylic materials generally may have mechanical and physical properties (e.g., a glass transition temperature of less than about 37° C., a Young's modulus of less than 60 MPa, relatively-high elongation at break of greater than 100%, low tackiness, etc.) suitable for foldable intraocular lenses. But, they generally have a refractive index higher than 1.50 but lower than 1.56. As such, those known acrylic materials may have limited use as microincision intraocular lenses because of the thicker lens optic necessary to achieve a given refractive power.
However, with increases in the refractive index of a soft hydrophobic acrylic material, glistenings (or microvacuoles) may become more apparent in IOLs made of such a material. Glistenings are tiny inclusions of water present within the matrix of an IOL material and are visible due to differences in refractive indices between the IOL material and water within the IOL material. It is reported that polyethylene glycol (PEG) dimethacrylates and/or PEG mono-(meth)acrylate can be used to improve glistening resistance of hydrophobic acrylic formulations. See, for example, U.S. Pat. Nos. 5,693,095, 6,353,069, and 8,449,610. But, in order to minimize its adverse effects on the refractive index of acrylic materials, low amounts of PEG dimethacrylate or PEG mono-(meth)acrylate concentrations are often required. Addition of PEG dimethacrylates or PEG mono-(meth)acrylates also tends to decrease the modulus and tensile strength of the resulting copolymer.
Therefore, there is a need for a soft hydrophobic acrylic material having a refractive index higher than that of known acrylic materials, glistening resistance, and physical and mechanical properties suitable for making intraocular lenses.